• P-series runs every other day.
• Z-Series runs approximately every three days.
  
  • BR cable/phase cal problem
    
    • Maintenance visit in late August 2023 at first seemed to have fixed the cable cal problem at BR, there was only one observation at the end of August and one in October that still had jumps in the cable cal but every other observation in September and October has looked okay. However, in November the cable cal problem began appearing again.
    • USNO reports that BR cable cal was less of an issue in March and April.
      • VLBA has noticed an increase in cable cal jumps in recent weeks. They appear to occur around the same times each day, 2000 and 0800 UT. Site tech speculates late afternoon heat and overnight cooling is causing expansion and contraction of cables.
  • SC began having a cable cal problem in June 2023. Still being investigated.
• Q-series intensive observations at MK run on weekends.
• I-series "Holiday" intensive observations at MK, substituting for Kokee on federal holidays.
  • MK will substitute for KK in regular I-series intensives for a period while a receiver replacement is made at KK (see below).
  • MK substituting for KK in late July/early August due to their fiber being damaged.

• UG005 did not observe their requested 16 hour session, only their 24-hour session.
• Q-series request asked for ten sessions, five weekends, but there are only four weekends in July. VLBA pre-monthly report reduced it down to eight sessions and requested hours dropped by two hours.
• 15 P-series were requested, 17 were scheduled but one was canceled due to a mechanical issue at HN.
• 10 Z-series were requested, 11 ran.
• UF006 requested 24 hours, used 23.5 hours.
• MK substituted for KK on five extra I-series observations, given a cost multiplier of 2.
• UD019 G was cut short when an HVAC failure in the DSOC server room made it impossible to continue monitoring the observation so it was terminated early. Service was not restored until the next morning too late to resume the observation. The missing time was not counted as backlog though it could be if a reobservation is requested in August.

• MK substituting for KK in I-series observations on Mondays and Tuesdays until KK fiber is repaired. Late addition to request so given a cost factor of 2.

• New schedule for P-series observations - Tuesday and Thursday at usual time, both Saturday and Sunday following the Q-series observations.

• Wildfires near KK delayed some repair work on a servo and then also took out their fiber connection the week of July 22.
  • MK substituted for KK July 25, 29, 30, 31.
  • Fiber repair may take a while, MK will continue to substitute on Mondays and Tuesdays.
• KK will be down at some point in October/November for six to eight weeks for a receiver replacement.
  
  • Plan looked to be to have MK observe the I-series intensives on Monday, Tuesday and Thursdays.
    • Some P-series observations would be scheduled to run before or after those sessions. Z-series would be nice to keep it to every three days, twice a week would be sufficient.
• Data ingest of IVS data to NRAO/Socorro in support of USNO backup correlator operations:
  • We will do a monthly test of the backup correlator by correlating a WZ-KK intensive. .
    
    • Future tests: August 14, September 4, October 1, November 6, December 4
  • Further use of the backup correlator in the processing of P-series and Z-series observations has been proposed.
    • Eventual goal would be to see a demonstration of these being processed on the backup correlator without the involvement of any DC-based USNO personnel.
    • Some testing might involve using the VLBA correlator rather than the backup correlator.
    • Will be easier for VLBA to handle after the deployment of the e-transfer filesystem later in 2024.
      • etc/etd will be the only transfer software initially supported by the e-transfer system.
      • Kokee will need to be asked to change to this software for the COOP tests. Wetzell has already switched to it.
    • This will hopefully transition into the ability to do bigger projects for USNO at DSOC such as the 24-hour R4 observations.
    • Testing has been done on both P and Z series observations with the backup correlator.
      • Storage space in the datacopy areas is insufficient to hold data from a P series and a Z series at the same time.
      • Data transfer rates were exceptionally slow, probably due to using rsync because tsunami and etc/etd were not available to USNO users on gygax.
        • Will need to get USNO access to the new transfer software before further testing can be done.
        • Probably will have to wait for e-transfer setup to be ready, hopefully in September?
  • USNO would like to be able to check automatically if the backup correlator is up or down but are unable to do so, can NRAO set something up for this?
    
    • Might have to wait for e-transfer to be operational at NRAO due to internet security concerns.
• Replacements of the Xcubes with DBS units
  
  • Installs were completed on May 2.
  • New software will ultimately cause a change in the naming structure of data files and PFB (Mark5B) data format will no longer be supported, instead it will be converted on the fly to VDIF format.
    
    • Software changes will need further testing before deployment. First iteration of the updates may not change naming structure of data files, may also not include the PFB->VDIF format.
• Higher speed network connections to HN and MK opens the possibility of realtime correlation of intensives.
  
  • Neither Washington correlator nor NRAO set up to do it yet.
    
    • Blocking issue for NRAO is mostly network speed into the correlator. This will probably be another thing that has to wait for the e-transfer hardware to be installed.
      • There also appears to be a bottleneck at the switch into the DSOC, that may need to be upgraded too.
        • New switch is in-house at DSOC, installation TBD.
    • USNO made some upgrades to their correlator's networking, up to ~2.5 Gbps on an individual transfer, but still not quite fast enough to do realtime transfers. Further upgrades are being worked on - probably will have to wait for the v3 correlator. USNO is getting a new data server for e-transfer, don't know if it will provide enough overhead to allow for realtime. Might know more next month.
      • No update.
• Is it possible to reduce the latency on 24-hr geodetic USNO-only sessions, with a goal of a latency between the completion of observation to analyzed result under 7 days?
  • E-transfer not really practical at this time so expedited shipping of disk packs is needed.
  • Might be limited to just attempting it for one of the two observations per month.
  • Record of time to correlation:
    
    • first year of observations (UD011 AA - AR) average time was 9 days. (Specifics can be found in minutes of previous meetings.)
    • UD011 AS 9 days, UD011 AT 11 days, UD011 AU 6 days, UD011 AV 12 days, UD011 AW - 6 days, UD011 AX - 12 days, UD011 AY - 9 days, UD011 AZ - 15 days, UD011 BA - 7 days, UD011 BB - 17 days, UD011 BC - 8 days, UD011 BD - 20 days, UD011 BE - 8 days, UD011 BF - 18 days, UD011 BG - 16 days, UD011 BH - 13 days, UD011 BI - 9 days, UD011 BJ - 11 days, UD011 BK - 9 days, UD011 BL - 13 days, UD011 BM - 11 days, UD011 BN - 14 days due to a recorrlelation being necessary, UD011 BO - 8 days, UD011 BP - observed July 29, waiting on disk packs.
• New IVS session code naming structure change in 2024
  • On NRAO's side, the Mark6 disk pack shipping/tracking program Packtrack has some problems with lengthy project codes but there are workarounds. This would only affect any intensives which get correlated in Socorro off of disk packs, currently there are none.
    • Plans are being developed in NRAO to overhaul Packtrack to cover things such as longer project codes and e-transferred data.
    • Packtrack will need to be rewritten to work under more up-to-date versions of Linux OS before other changes can be implemented.
      • The rewrite has been postponed to FY25 due to a lack of resources.
  • IVS will continue to use the existing shorter naming structure through all of 2023 into 2024.
    
    • USNO notes they are using the longer naming structure in correlation and archiving of data but will probably hold off on using it for observations until after IVS makes the switch.
      • No firm date yet for IVS to make the switch, still working on software.
        • Might start using longer codes on some intensive observations soon? But not all of them immediately, depends on software developments. Goal is to be fully on the new naming convention before FY25.
        • USNO doesn't think any have started using the longer names yet.
  • USNO sent some representative "new style" IVS observing codes for NRAO to run through its software looking for any unexpected problems.
    • Test NT2022224 AAA ran on Aug 12, 2022.
    • DiFX does have some project code length limitations, a modified trunk version of has been made for the correlation and the change will hopefully go into the next release (DiFX 2.8,which has now been released.)
      • There is an issue with Mark4 data, it does impact some USNO data (though not VLBA data).
      • USNO not using DiFX 2.8 yet. Also believe that 2.8 has a problem with mixed mode?
    • SCHED also has some project code length limits but SKED and VieSched ++ may not?
    • Some minor issues were found with archiving of data and some automated emails truncated the longer project code.
      • Xcube/DBS recording software does look at project codes to determine to record or not, will need to be addressed.
        • Z2024160A was observed June 8, the DBS units did not catch the longer project code name.
        • Test did run through USNO's side with no issues.
• Can some kind of acknowledgement be added to USNO data in the NRAO data archive indicating USNO's involvement?
  • Learned in mid-April that this has been pushed back to development cycle AAT 4.4.1 which is expected out in November 2024.
    
    • Walter was able to get this pushed up to AAT 4.3.2 which is expected out in August 2024.
• Possible changes coming to login accounts on DBS modules, moving to a group USNO account rather than using individual accounts?
  • No ETA on if/when group accounts would be instituted.
  • NRAO is trying to move away from group accounts for cybersecurity reasons so things may remain with individual accounts.
• USNO-NRAO contracts:
  
  • V3 DiFX (correlator upgrade) contract awarded in March 2023.
    • Biweekly build status meetings between NRAO and USNO are being held Wednesdays.
    • Some issues in installing DiFX 2.6.1 and a reliance on Python2.
    • Still some issues, especially with needing some backwards compatibility with v2.5, but work continues.

Long term issues

• Next DiFX release (2.8.2?) - a blocker issue for moving on to the next version for NRAO and probably USNO too has been resolved so moving to testing phase of the next release candidate can happen. Meetings for that began in May, probably take a couple months to sort everything out. Will be first release of it through GIT, procedures haven't been established for that yet. USNO input should be directed to Walter. Not likely it will be out before next DiFX meeting in mid-September so October looks more likely.
• NRAO will at some point begin doing data downloads during and after observations and this could conflict with USNO's own data downloads of the intensives.
  • Currently NRAO is only regularly doing data downloads once a week during a post-maintenance day test. Sometimes this does come shortly after a Z-series observation during the night.
    • USNO has not noticed any problems with their data downloads even when this has been the case.
  • Data downloads are also being done during the Z-series and P-series observations for realtime fringe checks, but this ends when the observation does so would not interfere with the following data downloads by USNO.
  • Not worth tracking anymore? Hasn't caused any trouble.
• There's interest in having VLBA observe along with a VGOS session in "mixed-mode".
  
  • First IVS needs to move some correlation off to other correlators and then they can start considering adding more stations like VLBA to the VGOS observations.
    • Not ready to include VLBA yet. Still issues within IVS and mixed mode to address first.
    • Some mixed mode issues may have been resolved.
    • Might add some VGOS stations to RDV observations to see how that works, VLBA correlator should be able to handle it
• .Peculiar delays - VLBA has a delay compared to Kokee that perhaps should be checked out, maybe put some VLBA stations into a KK observation as tagalongs so comparisons can be made. Walter reached out to some people, says it looks like it would be a bigger effort than anticipated.
  
  • Possibility of adding KK to an RDV observation raised..
    • KK will be in the April 2024 RDV observation so could get data from that.
      • RV165 observed April 24. Has been correlated.
      • After USNO (or NASA?) does analysis a copy of the clock offsets can be provided to VLBA for comparisons.
        • USNO has started analysis. Still some work to do, this is a low priority item.
      • Kokee does have a different maser compared to last time VLBA correlated with them, might have an effect?
• Installation of new GPS receivers
  • Antennas have been installed at all VLBA sites.
  • No ETA on installation of the GPS receivers.
    • First site in late October possibly.
• USNO and IVS partners have challenges with creating VLBA-valid VEX files with the SKED and VieSched ++ software packages.
  
  • Tuning VLBA at certain frequencies requires the additional commented information, it's not found in standard VEX setups/catalogs.
  • What is the plan, if there is one, for removing the need for the additional information required by the VLBA?
    • VEX2 standard will cover the missing information for VLBA, though the scheduling software used will still need to have the right setups information.
    • Probably 2024 before VLBA might switch to using VEX2, hopefully before 2025.
    • Things are okay right now with standard USNO setups and observations, could become an issue if USNO starts using non-standard setups in new observations.
    • Some testing of VEX2 has begun at NRAO.
      • Some diagnostic observations have switched to vex2 for testing purposes.
      • Seems to be okay for some regular observing, pointing and other modes still need some work.
      • Sched 12 comes out fairly soon, NRAO will switch to using vex2 internally after that. Vex 1.5 will remain supported but once VNDA is installed and running in 2026 NRAO will probably transition fully to vex2.
      • USNO would like some examples of differences between vex 1.5 and vex2 to see what would need to change. Some efforts on this have started. Move this up to Open Issues.

• 200 Mbps minimum at each site
• 1 Gbps at PT, KP, OV, NL. FD will be upgraded to 1 Gbps in June (done?)
• 5 Gbps at HN
• 10 Gbps at LA,MK; BR should be upgraded to 10 Gbps but something is bottlenecking it to 2.5 Gbps.
• 600 Mbps at SC (download up to 400 Mbps)